1. Field of the Invention
This invention relates to new and useful control system and apparatus for catheads for controlling accurately the amount of torque applied to a threaded connection.
2. Brief Description of the Prior Art
There has been a long need for a control system for controlling accurately and rapidly the amount of torque applied to threaded connections by catheads in oil field operation.
Weiner et al. U.S. Pat. No. 4,199,032 discloses an apparatus for controlling the make up of a threaded connection which insures that a specified torque will not be exceeded. The apparatus consists of power tongs which pull against a fixed support and includes a comparator for comparing measured torque with a desired torque value and disengages make up of the connection when the measured torque exceeds the selected value.
McCombs et al. U.S. Pat. No. 4,208,775 discloses a method and apparatus for making threaded connections where the applied torque is monitored and when a reference torque is exceeded the number of turns is counted. The subsequent operation limits the number of turns of tightening the threaded connection to a predetermined percentage of the turns which would exceed the reference torque.
Rice U.S. Pat. No. 4,016,938 discloses a system for use with torque producing power tools which determines when a fastener has been driven to its yield point in tension and thereafter backing the fastener out sufficiently to establish a level of tension below the yield point.
Hannson U.S. Pat. No. 3,957,248 discloses a control for an air hoist operated by a pneumatic motor having a blow-off valve which vents at a predetermined load to limit the torque of the motor.
Conboy U.S. Pat. No. 3,933,388 discloses a fluid-operated, load-handling apparatus having an interlock control system including pressure sensitive valves which limit the operation of a pneumatic motor.
O'Leary U.S. Pat. No. 2,805,042 discloses a torque-limiting hoisting drum.
Fuelster et al. U.S. Pat. No. 3,497,787 discloses an automatic control for a mine hoist which accurately controls the position by control of an electric motor.
Himmelstein et al. U.S. Pat. No. Re. 28,899 (of U.S. Pat. No. 3,827,506) discloses a torque control for pneumatically operated nut drivers.
Hardiman et al. U.S. Pat. No. 3,939,920 discloses a tightening method and system for power wrenches which limits the application of torque to a predetermined percentage of a torque which would reach the yield point of the fastener being applied.
Bromell U.S. Pat. No. 3,662,842 discloses an automatic coupling system in which a sensing quill is used to operate a switch limiting the torque applied by the system and apparatus.